IPTV (Internet Protocol Television, interactive internet protocol television) is a technology that provides a home user with a variety of interactive services including a digital television by using a broadband IP network. The IPTV mainly provides a user with a video service, and therefore has a very high requirement on a transport network. Once the transport network fails to meet a transport quality requirement of the IPTV, quality degradation phenomena such as mosaic, a pause, and a skip of a video picture occur, which seriously affects QoE (Quality of Experience) of a terminal user. Therefore, once a problem occurs in the transport network, an IPTV service operator desires to quickly and timely locate which link where the problem occurs in the transport network, that is, to implement fault location.
In an existing IPTV network, a network fault is detected through an MDI (Media Delivery Index). Specifically, the MDI includes two measurement indicators, namely, a DF (Delay Factor) and an MLR (Media Loss Rate). A DF value indicates delay and jitter conditions of a tested video stream, and an MLR value indicates a packet loss rate in transmission of the tested video stream. After obtaining a DF value and an MLR value, each monitoring node sends, according to its own timing mechanism, the test value to a management center periodically; and by respectively comparing DF values and MLR values reported by different nodes periodically, the management center can obtain that a jitter occurs between which devices and a packet loss occurs between which devices. For example, upstream and downstream values are DF1 and MLR1, and DF2 and MLR2 respectively. If DF1=5 ms, MLR1=0; DF2=40 ms, and MLR2=5, it indicates that a jitter (DF) of video on an upstream device is small but a jitter (DF) on a downstream device is quite large, and it indicates that a jitter occurs between the two devices. Ideal IP video stream transmission requires that an MLR value should be zero. Because the MLR1 of the upstream device is equal to 0, it indicates that there is no packet loss in this period, while because the MLR2 of the downstream device is equal to 5, it indicates that a packet loss (5 TSs (Transport Stream) per second) occurs on the downstream device in this period, and a link between the upstream node and the downstream node is a faulty link.